MEMORY LECTURE - 13 DR. ZAHOOR ALI SHAIKH 1
MEMORYLECTURE - 13
DR. ZAHOOR ALI SHAIKH
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HIGHER FUNCTIONS OF BRAIN:LEARNINGMEMORYJUDGEMENTLANGUAGESPEECH
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WE WILL DISCUSS MEMORY UNDER THE FOLLOWING HEADINGS:WHAT IS MEMORY?WHERE IS MEMORY STORED?CLASSIFICATION OF MEMORYHOW STORAGE OF MEMORY OCCURS?MOLECULAR MECHANISM
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Cont….TERMINOLOGY USED (REMEMBER THE
WORDS)
RECALL MECHANISMCAUSES OF LOSS OF MEMORYHOW TO TEST THE MEMORY
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WHAT IS MEMORY? (LONG TERM)MEMORY IS STORAGE OF ACQUIRED
KNOWLEDGE FOR LATTER RECALLWE KNOW LITTLE ABOUT THE
MECHANISM OF MEMORY
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MEMORY INVOLVESRECEPTION OF INFORMATIONFORMATION OF MEMORY TRACE CONSOLIDATION OF MEMORY TRACERECALL OF MEMORY TRACE
SEQUENCE OF EVENTS IN MEMORYNEWLY ACQUIERED INFORMATION – SHORT
TERM MEMORY (USUALLY LOST) OR IT IS TRANSFERRED TO LONG TERM MEMORY BY REHERSAL – CONSOLIDATION INTO LONG TERM MEMORY
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WHERE IS MEMORY STORED?MEMORIES ARE STORED IN THE BRAIN AT
SYNAPSES BY CHANGING THE BASIC SENSITIVITY OF SYNAPTIC TRANSMISSION BETWEEN NEURONS. WE CREATE A MEMORY TRACE
MEMORY TRACE: THE NEURAL CHANGE AT SYNAPSES WHICH IS
RESPONSIBLE FOR RETENTION OR STORAGE OF KNOWLEDGE IS KNOWN AS MEMORY TRACE.
ONCE MEMORY TRACE ARE ESTABLISHED, THEY CAN BE ACTIVATED BY THINKING MIND TO REPRODUCE MEMORY
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WHAT PARTS OF BRAIN ARE RESPONSIBLE FOR MEMORY?
MEMORY TRACES OCCUR AT MANY REGIONS OF BRAIN AT CORTICAL AND SUBCORTICAL REGIONS. THERE IS NO SINGLE MEMORY CENTER
THE IMPORTANT MEMORY AREA ARE: CEREBRAL CORTEX (MOTOR,SENSORY,VISUAL
AUDITORY) PREFRONTAL CORTEX HIPPOCAMPUS & MEDIAL TEMPORAL LOBE LIMBIC SYSTEM THALAMUS CEREBELLUM
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IMPORTANTHIPPOCAMPUS – MAINTAINS RECORD OF
EVERYDAY EVENTS IN OUR LIFE.PERSON WITH HIPPOCAMPUS DAMAGE
ARE EXTREMELY FORGETFULL TO DAILY FUNCTIONING
HIPPOCAMPUS IS FOR SHORT TERM MEMORY
NOTE: IN ALZHEIMERS DISSEASE DAMAGE OCCURS TO HIPPOCAMPUS REGION THEREFORE LOSS OF SHORT TERM MEMORY
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MEMORY MAY BEPOSITIVENEGATIVE
o POSITIVEMEMORY:o IS ALSO CALLED SENSATISATION OR
FACILITATIONo IT IS DUE TO STORAGE OF MEMORY TRACES
& RECOLLECTION OF PREVIOUS THOUGHTS OR EXPERIENCES
o IT OCCURS DUE TO FACILITATION OF SYNAPTIC PATHWAYS
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NEGATIVE MEMORY:IT IS ALSO CALLED HABITUATION OR
INHIBITIONIT IS CAPABILITY OF BRAIN TO IGNORE THE
INFORMATION WHICH IS NOT IMPORTANTGREATER SHARE OF OUR MEMORIES ARE
NEGATIVE MEMORYIT IS DUE TO INHIBITION OF SYNAPTIC
PATHWAY•
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(FROM GUYTONS TEXTBOOK OF PHYSIOLOGY) CLASSIFICATION OF MEMORY:
1. SHORT TERM MEMORY• MEMORY WHICH LASTS FOR SECONDS TO MINUTES(UNLESS THEY ARE CONVERTED INTO LONG TERM
MEMORIES)Eg: TO REMEMBER TELEPHONE NUMBER 7 – 10 DIGITS FOR
SECONDS OR MINUTES, TILL YOU ARE THINKING ABOUT THE NUMBERS
2. INTERMEDIATE LONG TERM MEMORY:LASTS FOR MINUTES, HOURS, DAYS TO WEEKS, BUT
THEN THEY WILL BE LOST ( UNLESS CONVERTED TO LONG TERM MEMORY)
3. LONG TERM MEMORY:WHICH ONCE STORED CAN BE RECALLED UP TO
YEARS OR EVEN FOR WHOLE LIFEEg: NUMBER OF PRAYERS PER DAY
DAYS OF THE WEEK
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(FROM GANONGS REVIEW OF PHYSIOLOGY )
CLASSIFICATION OF MEMORY:
1.SHORT TERM MEMORY: WHICH LASTS FOR SECONDS TO HOURS –
HIPPOCAMPUS Eg: MEMORY OF FEW WORDS, NUMBERS,
LETTERS LIMITED TO 7 – 10 NUMBERS LIKE TELEPHONE NUMBERS, CAR NUMBER
2.LONG TERM MEMORY: WHICH LAST FOR DAYS, MONTHS, YEARS OR
LIFETIME
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ANOTHER TYPE OF MEMORY WORKING MEMORY:
IT INCLUDES MAINLY SHORT TERM MEMORY, THAT IS USED DURING THE INTELLECTUAL REASONING , BUT IS TERMINATED AS PROBLEM IS SOLVED. – PREFRONTAL LOBE IS INVOLVED
Eg: SEE THE TELEPHONE NUMBER , REMEMBER THE NUMBER WHILE PICKUP PHONE, DIAL THE NUMBER AND TALK ABOUT THE PROBLEM Eg: Examination Preparation
NOW IT IS THOUGHT THAT INTELLIGENCE DEPENDS ON WORKING MEMORY.
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MEMORY CLASSIFICATION ACCORDING TO THE TYPE OF INFORMATION: DECLARATIVE MEMORY OR EXPLICIT
MEMORY IT IS MEMORY OF SURROUNDINGS, EVENTS,
TIME, Eg. WE PLAYED FOOTBALL GAME TODAY DECLARATIVE MEMORY IS DEPENDENT ON
HIPPOCAMPUS
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MEMORY CLASSIFICATION ACCORDING TO THE TYPE OF INFORMATION [CONT]:
SKILL MEMORY OR IMPLICIT MEMORY IT IS LEARNING OF SKILLS Eg. LEARNING
FOOTBALL, HOW TO HIT OR STRIKE MOVE THE BALL etc.
SKILLS ONCE ACQIRED BECOME AUTOMATIC RETENTION OF SKILLS DOES NOT INVOLVE
HIPPOCAMPUS BUT CEREBELLUM, PRIMARY MOTOR CORTEX, SOMATOSENSORY CORTEX, VISUAL PROCESSING AREAS
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HOW MEMORY IS STORED:MEMORY DOES NOT RESIDE IN A SINGLE
NEURON BUT CHANGES OCCUR IN THE PATTERN OF SIGNALS TRANSMITTED ACROSS SYNAPSES WITHIN A NORMAL NETWORK
SHORT TERM MEMORY:INVOVES TRANSIENT MODIFICATION IN
THE FUNCTION OF SYNAPSES Eg: AMOUNT OF NEUROTRANSMITTER RELEASED IN RESPONSE TO STIMULATION
EXPERIMENTS ARE DONE IN SEA SNAIL (APLYSIA)Eg. HABITUATION OR INHIBITION & SENSITIZATION OR FACILITATION 17
APLYSIA
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MEMORY SYSTEM THAT HAS BEEN DISCOVERED IN THE SNAIL APLYSIA
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APLYSIA
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LONG TERM MEMORY:INVOVES PERMENANT STRUCRURAL
CHANGES BETWEEN EXISTING NEURONS IN THE BRAIN DUE TO ACTIVATION OF SPECIFIC GENES THAT CONTROL PROTEIN SYNTHESIS. THESE PROTEINS CAUSE : FORMATION OF NEW SYNAPTIC CONNECTIONS GREATER BRANCHING ANDF ELONGATION OF
DENDRITES IN NERVE CELL IN BRAIN AREAS INVOLVED FOR MEMORY STORAGE.
INCREASE NO. OF VESICLES IN PRESYNAPTIC NEURON
INCREASE NO. OF SIGNAL TRANSMISSION
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LONG TERM MEMORY:NAME OF POSITIVE REGULATORY
PROTEIN FOR LONG TERM MEMORY IS “CREB” , A MOLECULAR SWITCH THAT ACTIVATES LONG TERM MEMORY STORAGE.
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CONSOLIDATION OF MEMORY: (TO REMEMBER)FOR SHORT TERM MEMORY TO BE
CONVERTED INTO LONG TERM MEMORY IT MUST BE CONSOLIDATED
CONSOLIDATION OCCURS BY REPEATEDLY ACTIVATING THE SHORT TERM MEMORY, WHICH WILL INITIATE CHEMICAL, PHYSICAL AND ANATOMICAL CHANGE IN THE SYNAPSES THAT ARE RESPONSIBLE FOR LONG TERM MEMORY
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CONSOLIDATION OF MEMORY: (TO REMEMBER) [CONT]
IT TAKES 5 TO 10 MINUTES FOR MINIMAL CONSOLIDATION AND ONE HOUR OR MORE FOR STRONG CONSOLIDATION
SOME FACTORS PREVENT CONSOLIDATIONHEAD INJURY – BRAIN CONCUSSIONDEEP GENERAL ANAESTHESIA – SUDDENLY
APPLIEDELECTRICALLY INDUCED BRAIN
CONVULSIONS
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LOSS OF MEMORY (AMNESIA): RETROGRADE AMNESIA
LOSS OF MEMORY BEFORE THE ACCIDENT
ANTEROGRADE AMNESIA LOSS OF MEMORY AFTER THE ACCIDENT
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AMNESIA
PASTPRESENTACCIDENT
RETROGRADE MEMORYBEFORE THE ACCIDENT
ANTEROGRADE MEMORYAFTER THE ACCIDENT
• HIPPOCAMPUS REMOVAL (FOR TEMPORAL LOBE EPILEPSY) OR LESION – MAINLY ANTEROGRADE AMNESIA
• THALAMIC LESION MAINLY RETROGRADE AMNESIA• THEREFORE IT SHOWS HIPPOCAMPUS IS RESPONSIBLE
FOR NEW MEMORIES AND THALAMUS STORES OLD MEMORIES
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TERMINOLOGY USED IN MEMORY:MEMORY TRACE: THE NEURAL CHANGE
RESPONSIBLE FOR RETENTION OF KNOWLEDGE IS KNOWN AS MEMORY TRACE
SENSITIZATION OR POSITIVE MEMORY OR FACILITATION
NEGATIVE MEMORY OR HABITUATION OR INHIBITION
SHORT TERM MEMORYLONG TERM MEMORY
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TERMINOLOGY USED IN MEMORY [CONT]:
WORKING MEMORYMEMORY ACCORDING TO TYPE OF
INFORMATION DECLARATIVE MEMORY SKILL MEMORY
AMNESIA OR LOSS OF MEMORY RETROGRADE AMNESIA ANTEROGRADE AMNESIA
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RECALL OF MEMORY:ALL COMPONENTS OF MEMORY ARE
BROUGHT TO CONSCIOUSNESS RECALL OF MEMORY BY . . . .
SIMILAR SCENE SIMILAR SOUNDSIMILAR SMELLSIMILAR VIEWSIMILAR WORDS
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DEMENTIAIMPAIMENT OF
MEMORY, INTELLIGENCE AND PERSONALITY WITHOUT IMPAIRMENT OF CONSCIOUSNESS
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HOW TO TEST THE MEMORY?RECENT MEMORY TEST:
GIVE NAME AND ADDRESS TO REMEMBER (7 – 10 WORDS) THEN ASK 5 MINUTES LATER OR
GIVE THREE ITEMS WITHIN THE ROOM AND ASK THE PATIENTS TO REPEAT THEIR NAMES AFTER 5 MINUTES
DISTANT MEMORY TEST: ASK IMPORTANT DATE WHICH PATIENT
KNEW THE ANSWER AND CLINICIAN ALSO KNOWS THE ANSWER Eg. NATIONAL DAY,
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INTRESTING INFORMATION3 SPECIES HAVE BRAIN LARGER THAN
HUMANSI. ELEPHANTII. PORPOISEIII. WHALE
BUT IN RELATION TO BODY WEIGHT HUMAN BRAIN IS LARGE
WEIGHT OF A HUMAN BRAIN IS ABOUT THREE POUNDS OR 1.5 KG
ALCOHOL CAUSES LOSS OF RECENT MEMORYPATHALOGICAL CHANGES ARE SEEN IN
MAMILLARY BODIES WHICH HAS EXTENSIVE CONNECTIONS TO THE HIPPOCAMPUS 33
IMPORTANT AREAS FOR . . . SHORT TERM MEMORY – HIPPOCAMPUS,
MEDIAL TEMPORAL LOBELONG TERM MEMORY – NEOCORTEXDECLARATIVE OR EXPRESSIVE OR EXPLICIT
MEMORY – HIPPOCAMPUSSKILL OR IMPLICIT OR NON DECLARATIVE
MEMORY – CEREBELLUM, BASAL GANGLIA.WORKING MEMORY – PREFRONTAL CORTEXMEMORIES VISUAL, OLFACTORY, AUDITORY
ARE LOCATED IN RESPECTIVE CORTICAL REGIONS.
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ALZHEIMER DISEASE LOSS OF RECENT MEMORY AFFECTED AREAS – HIPPOCAMPUS,
MAMMILLARY BODY, ANT. HYPOTHALAMUS, PREFRONTAL CORTEX, NEOCORTEX
THERE IS PROGRESSIVE LOSS OF SHORT TERM MEMORY AT THE AGE OF 50 YEARS OR AFTER
NEUROTANSMITTER ACETYLCHOLINE IS LOST DUE TO LOSS OF SYNAPSES AND NEURONS CAUSED BY TOXIC PEPTIDE A β1-40 AND A β1-42
SENILE DEMENTIANOTE SENILE DEMENTIA OCCURS AFTER THE
AGE OF 65 YEARS AND IT IS SLOWLY PROGRESSIVE
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MEMORY ESSAY QUESTION EXAM – RECALL
MEMORY (SUBJECTS PRODUCE INFORMATION ON THEIR OWN)
MCQ EXAM – RECOGNITION - SUBJECTS IDENTIFY PREVIOUSLY LEARNED INFORMATION
RESEARCH SHOWS RECOGNITION IS EASIER THAN RECALL
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MEMORYMETHOD OF STUDY IN HUMANS
PET SCAN (POSITRIN EMISSION TOMOGRAPHY) MEASURES LOCAL GLUCOSE METABOLISM
WHICH IS PROPORTIONATE TO THE NEURAL ACTIVITY
fMRI (FUNCTIONAL MAGNETIC RESONANCE IMAGING) Measures local amount of oxygenated blood which
tells about the activity of brain
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HOW IMPORTANT IS MEMORY . . .IMAGINE IF WE WERE WITHOUT IT WE
WOULD NOT RECOGNISE ANYONE, WE WOULD REMEMBER NOTHING AND WOULD HAVE NO RECOLLECTION OF THE EVENTS OF OUR OWN LIVES. WE WOULD HAVE LACK OF KNOWLEDGE AS NEW BORN BABIES.
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THANK YOU
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